Electromechanical steering system for a vehicle

ABSTRACT

An electromechanical steering system for a vehicle comprises a steering shaft, which is mounted rotatably in an accommodating space of a steering housing, and an electric motor, which, acts upon steering shaft over a transmission. Furthermore, a coil spring housing with a coil spring is provided in the accommodating space. The accommodating space is divided by a partition into a section accommodating the coil spring and a section accommodating the transmission. A damping almond is integrated in the partition. The housing of the coil spring forms part of the partition.

BACKGROUND OF THE INVENTION

The invention relates to an electromechanical steering system for avehicle.

DE-A1-1972853 discloses such an electromechanical steering system. Forsupporting the steering moment produced by the driver, the steeringsystem has an additional system, which is driven by an electric motorand acts on the steering shaft of the steering system and meshes withthe steering shaft over a worm gear, as a result of which an additionalmoment, supporting the steering motion of the driver, can be introducedinto the steering shaft. In order to obtain information about thesteering angle and the steering angle speed, a steering angle sensor,the signals of which are transferred by a coil spring to a controldevice in the housing, is provided on the steering shaft. The coilspring is located in a coil spring housing and is connected at one endwith the sensor, rotating with the steering shaft, and, at the other,with a socket attached to the housing, over which an electrical contactto the steering device can be produced. The coil spring is in a positionto carry out, without damage, the steering shaft rotations occurringduring the driving operation.

The coil spring housing with the coil spring disposed therein describedin DE-A1-19228513 is located in an accommodating space within a steeringhousing, in which the steering shaft is mounted rotatably. The wormgear, which transfers the rotational movement of the electric motor tothe steering shaft for supporting the steering movement, is located inthe accommodating space in the steering housing. So as to preventcontamination of the sensor or of the contact sites of the sensor or ofa magnet assigned to the sensor by the lubricating grease of the wormgear, a partition is provided there, which divides the accommodatingspace into a section, which accommodates the coil spring, and a section,which accommodates the transmission. The housing of the coil springforms a part of this partition.

The DE-A1 197 55 094 also discloses such an electromechanical steeringsystem.

The coil spring housing with the coil spring disposed therein is locatedin an accommodating space within a steering housing, in which thesteering shaft is mounted rotatably. The worm gear, which transfers therotational movement of the electric motor to the steering shaft forsupporting the steering movement, is located in the accommodating spacein the steering housing. It is necessary to pay attention so that thesensor or the contact sites of the sensor or a magnet, assigned to thesensor, are not contaminated by the lubricating grease of the worm gear.In addition, the coil springs, including the coil spring housing and thesteering angle sensor, also represent a source of danger for the wormgear, since the latter can be blocked in the event that a componentwithin the accommodating space becomes detached or breaks off.

SUMMARY OF THE INVENTION

It is an object of the invention to construct a generic, operationallysafe steering system for a vehicle with simple means.

The electromechanical steering system has an accommodating space, whichis divided by a partition into two separate sections, a damping elementbeing integrated in the partition for damping vibrations of the coilspring housing and the coil spring housing, especially the bottom of thecoil spring housing, forming part of the partition. This construction isdistinguished by a series of advantages:

Because of the division into two separate sections, in which in eachcase the transmission of the electric motor and the coil spring areaccommodated, on the one hand, the danger is prevented that thelubricating grease of the transmission comes into contact with thesensor or the contact sites of the sensor or a magnet assigned to thesensor, which could be damaged thereby, and, on the other, that a partof the coil spring, which has accidentally become detached, or of thecoil spring housing or of a component disposed thereon gets into thedenticulation of the transmission, which could become blocked therebyand therefore also result in the blockage of the steering. The partitioncan be inserted in the accommodating space in the steering housingduring the installation of the steering system: on the other hand, it isnot necessary to provide a partition in the accommodating space from thevery start.

Since the bottom of the coil spring housing forms part of the partition,a particularly compact construction is achieved with this advantageousembodiment, because the bottom of the coil spring housing lies in acommon plane of separation with the further sections of the partition.

The damping element, integrated in the partition, decreases vibrationsof the coil spring housing, especially radial vibrations, which act inthe radial direction transversely to the steering axis of the steeringsystem. The damping of the vibrations results in a reduction of thenoise level and, in addition, improves the service life of the coilspring housing including that of the coil spring disposed therein, sincethe mechanical stresses are reduced.

In an appropriate further development, the damping element isring-shaped and disposed in the section of the partition between theradial outside of the coil spring housing and the inside of theembracing radial outer wall of the accommodating space. In aparticularly simple embodiment, the damping element is a gasket orcomprises a gasket, the rubber of which has vibration-dampingproperties. This embodiment furthermore offers the advantage that thepartition can be installed easily in the accommodating space of thesteering housing.

The damping element, especially the seal constructed as a gasket, can bebonded on a gasket support or sprayed on the latter. The gasket supporthere is either identical with the coil housing or is a support ring,which is constructed separately but connected with the coil housing.

The damping element, especially the gasket, can also compensate fordifferent thermal expansions of the coil housing and of the inner wallof the accommodating space.

Further advantages and appropriate embodiments may be inferred from theclaims, the description of the FIGURE and the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE shows a steering housing in section of an electromechanicalsteering system for a vehicle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The steering system 1 for a vehicle is constructed as anelectromechanical system and comprises a steering shaft 2, which isdisposed in a steering housing 3 and over which the steering actuationof the driver is transferred to the steered wheels. To support thesteering actuation, a supportive torque of an electric motor 7 isintroduced over a rotor 6 over a transmission 4, which comprises a wormwheel 5 revolving with the steering shaft 2. The electric motor 7 can beadjusted by a control device as a function of the state variables andthe operating variables of the vehicle, especially of the steeringsystem. The rotor 6 of the electric motor 7 or a component 6, driven bythe rotor of the electric motor represents, in relation to the wormwheel, a driving wheel, the rotation of which is transferred to the wormwheel 5, which is disposed coaxially within the steering shaft 2 andfurther to the steering shaft, which is disposed coaxially with thesteering shaft 2, and further to the steering shaft 2.

In the steering housing 3, an accommodating space 8 is provided, inwhich the steering shaft 2 is mounted rotatably. The transmission 4between the electric motor 7 and the steering shaft 2 is also disposedin the accommodating space 8, as is optionally also the electric motor7.

Furthermore, a coil spring housing 9 is provided in the accommodatingspace 8. It is constructed ring-shaped, seated on the steering shaft 2and disposed coaxially with the latter. The coil spring housing 9 has afirst housing section 9 a, which is adjacent with the steering shaft 2,with which it rotates, as well as a second housing section 9 b, which isconnected with the steering housing 3, so that the housing sections 9 aand 9 b can be rotated relative to one another in correspondence withthe steering motion of the steering shaft 2.

In the annular space of the coil spring housing 9, a coil spring 10 iswound spirally. One end 10 a of the coil spring 10 is connected firmlywith the section 9 a of the coil spring housing rotating with thesteering shaft 2 and communicates with a torque sensor 11, which is alsodisposed in the accommodating space 8 and rotates with the steeringshaft 2. The second end 10 b of the coil spring is connected firmly withthe housing section 9 b of the coil spring housing, which is connectedfirmly with the steering housing 3. The second coil spring end 10 b isconnected, in particular, with a socket 12, which advisably is seated onthe radial outer side of the coil spring housing 9 on the housingsection 9 b and is constructed to accommodate the plug, over which thesignals, which are transmitted over the coil spring 10 and containsteering angle information from the torque sensor 11, are supplied to aregulating and control unit for further evaluation.

The accommodating space 8 in the steering housing 3 is divided into twowith two sections 8 a and 8 b, which are divided by a partition 13. Thepartition 13 extends between the steering shaft 2 and the outer wall 14of the steering housing 3, which radially embraces accommodating space8, the two sections 8 a and 8 b of the accommodating space, separated bythe partition 13, being divided appropriately in such a manner, thattransfer of dirt and of loose parts between the two sections of theaccommodating space is prevented.

The partition 13 is formed by a radial wall side of the housing section9 b of the coil spring housing 9, which is firmly connected with thesteering housing 3, a radially extending support ring 15 slipped ontothe housing section 9 b and an annular gasket 16, which is bonded ontothe support ring 15 and fills the gap remaining between the support ringand the inside of the outer wall 14 of the steering housing. The radialpart of the housing section 9 b, the support ring 15 and the gasket 16lie in a common partitioning plane here. The gasket 16 lies against theinside of the outer wall 14 of the steering housing 3, as a result ofwhich a complete separation between the two sections 8 a and 8 b of theaccommodating space 8 is achieved. Because of the pliability and dampingproperties of the gasket 16, damping of radial vibrations and impacts,emanating from the steering shaft 2 and spreading out over the coilspring housing 9, is achieved. The vibration-damping properties of thegasket 16 can be improved by an appropriate structural configuration ofthe gasket, for example, by a sealing lip, which protrudes from the bodyof the gasket 16 and lies against the inside of the outer wall 14.

In the first section 8 a of the accommodating space 8, there is thetorque sensor 11 as well as the greater part of the coil spring housing9, including the coil spring 10, which is wound up therein. The part ofthe partition 13, assigned to the coil spring housing 9, is formed bythe bottom of the coil spring housing. In the second section 8 b of theaccommodating housing 8, the transmission with the worm wheel 5 and therotor 6 or a component 6, acted upon by the rotor, and optionally alsothe electric motor 7 are disposed.

Centering of the coil spring housing 9 in the accommodating space 8 isachieved by the partition 13, by means of which the friction between therevolving components and the components attached to the housing, as wellas the development of noise are reduced.

LIST OF REFERENCE SYMBOLS

-   1 steering system-   2 steering shaft-   3 steering housing-   4 transmission-   5 worm wheel-   6 rotor-   7 electric motor-   8 accommodating space-   8 a section-   8 b section-   9 coil spring housing-   9 a housing section-   9 b housing section-   10 coil spring-   10 a end-   10 b end-   11 torque sensor-   12 socket seat-   13 partition-   14 outer wall-   15 support ring-   16 gasket

1. Electromechanical steering system for a vehicle, with a steeringshaft, rotatably mounted in an accommodating space of a steeringhousing, and an electric motor acting upon the steering shaft over atransmission, a coil spring housing with a coil spring being disposed inthe accommodating space, the accommodating space being divided by apartition into one section accommodating the coil spring, and anothersection accommodating a transmission, the coil spring housing formingpart of the partition, and a damping element comprising a seal with asealing lip, said sealing lip being disposed at a distance from asealing element of the seal, said damping element being disposed againstthe inside o the outer wall of the steering housing and being integratedin the partition.
 2. The steering system of claim 1, wherein the dampingelement is ring-shaped and disposed between the radial outside of thecoil spring housing and the embracing radial outer wall of theaccommodating space in the steering housing.
 3. The steering system ofclaims 1 or 2, wherein the damping element is slipped onto the coilspring housing.
 4. The steering system of claim 1, characterized in thatthe wherein the seal is accommodated in a seal support.
 5. The steeringsystem of claim 4, wherein the seal is sprayed onto the seal support. 6.The steering system of claim 4, wherein the seal is bonded onto the sealsupport.
 7. The steering system of one of the claims 4 to 6, wherein theseal support is the coil housing.
 8. The steering system of one of theclaims 4 to 6, wherein the seal support is a support ring constructedseparately from the coil housing and connected with the coil housing. 9.The steering system of claim 1 or 2, wherein a sensor connected torotate with the steering shaft is provided to determine the steeringangle in the section of the accommodating space accommodating the coilspring.
 10. The steering system of claim 1 or 2, wherein thetransmission between the electric motor and the steering shaft is a wormgear.